Controller Method

    public function postExistingCompanyToNetwork(AddExistingCompanyToUsersNetwork $request)
    {
        if ( ! $company = $this->company->postToUsersNetworkByUuid($request, $this->user) )
        {
            return Redirect::back();
        }

        return Redirect::route('network');
    }

Test

        $company = Mockery::mock('App\Repositories\Company\CompanyInterface');

        $response = $company->shouldReceive('postToUsersNetworkByUuid')->once()->andReturn('Fishsticks');

        $this->app->instance('App\Repositories\Company\CompanyInterface', $company);

        $this->action('POST', 'NetworkController@postExistingCompanyToNetwork');

        $this->assertRedirectedToRoute('network');